Patients who have suffered strokes affecting the right postenor parietal cortex often exhibit the syndrome of hemispatial neglect, an attentional deficit causing the individual to ignore the opposite side of the body and extrapersonal space. A common part of this syndrome is double simultaneous stimulus extinction (DSSE), wherein awareness of an object in contralateral hemispace is blocked only when a second object is simultaneously presented in the ipsilateral hemispace. We are exploring the mechanisms of visuospatial perception by testing patients with hemispatial neglect in a DSSE paradigm which uses overlying optic flow stimuli to trigger perceptual reorientation towards the neglected hemifield. The goal is to explore the dynamics of spatial orientation in subjects with various impairments of orientation attributable to lesions located in different parts of posterior parietal cortex. This project is operating as a collaboration between members of different units within the the University of Rochester Department of Neurology at Strong Memorial Hospital (Dr. Duffy from the Neuro-ophthalmology Unit and Dr. Langfitt from the Neuropsychology Unit). We are currently developing a separate limb of this study in collaboration with Dr. John G. Schmidt of St. Mary's Hospital Neurorehabilitation Unit in Rochester.